Video productions involve frequent scene changes. Such changes may be accomplished by simply splicing scenes together to create an abrupt cut between scenes, or may alternately involve gradual changes known as transition effects. Many types of transition effects are well known in the video industry, including fades, wipes (left-to-fight, fight-to-left, top-to-bottom, etc.), patterns, etc. Typically, these transition effects are generated directly against the analog video signal by analog electronic circuitry, with different circuitry being required to create each family of effects. The hardware required to create such transition effects is costly, and in practice only economically feasible in commercial applications.
Recent advances in microprocessors and random access memory have made it possible to manipulate images in digital form. This in turn has lead to a new class of applications known as "multimedia," which combine audio, video, and text to create presentations. As part of their image processing capabilities, some of these multimedia applications include facilities to create transition effects. These applications represent an improvement over traditional video transition effects generators in that they do not require special hardware; instead they use computer programs to create transition effects by directly manipulating the digital representations of images stored in computer memory.
However, while the programming solution to transition effects is an improvement over its hardware ancestor, it is not without limitations. The chief drawback of program transition effects is that each effect requires its own coded procedure. Thus, to provide a variety of effects a substantial investment in programming is required. Additionally, complex effects require equally complex programming, further increasing cost. Finally, regardless of how many effects are provided, no capability is available to create custom effects adapted to a specific user requirement, short of coding an additional program.
Thus, there has heretofore existed an urgent need for a computer-based system capable of providing an extensible library of transition effects without the use of separately coded procedures.